A washing machine washes laundry using the surfactant action of detergent, a water stream generated via rotation of a washing tub or a washing blade, shocks applied by the washing blade, or the like. The washing machine performs washing, rinsing and/or dehydration processes to remove contaminants adhering to laundry, e.g., clothes, using the interaction of water and detergent.
A washing machine includes a casing defining the appearance of the washing machine, an imperforated tub, which is disposed in the casing in a suspended state, and a perforated basket or drum, which is rotatably disposed in the tub. Since the basket and the tub are contaminated due to various causes such as scaling, slime, solidified detergent or the like with repeated use for an extended time, it may be necessary to periodically carry out an operation of washing the tub (hereinafter, an operation of cleaning the tub and components disposed in the tub is defined as “tub washing”) to remove the contamination sources.
A tub washing is performed by supplying a sufficient amount of water to a tub to simultaneously wash the upper and lower parts of the tub. Since there is a difference in accumulation of pollutants between the upper and lower parts of the tub, the upper and lower parts of the tub should be respectively washed in different manners in order to thoroughly clean both the upper and lower parts of the tub. However, even though components such as a pulsator, a hub for coupling a basket to a rotating shaft, a filter and the like having greater amount of pollutants, are disposed at a lower portion of the tub, the washing machine performs tub washing without discriminating between the upper and lower parts of the tub, resulting in inefficient washing.